Bipolar plasma catheter

ABSTRACT

The present disclosure provides a plasma catheter including a tubular member; a conductive cylindrical member; a first electrode; and a second electrode. The tubular member defines a longitudinal lumen therethrough and has a proximal portion and a distal portion. The conductive cylindrical member is disposed at the distal portion of the tubular member. The first electrode is embedded in a first side of the tubular member and coupled to the conductive cylindrical member. The second electrode is embedded in a second side of the tubular member diametrically opposed to the first side. The second electrode is offset from the tubular member and aligned with a center axis defined by the conductive cylindrical member.

BACKGROUND

Technical Field

The present disclosure relates to plasma devices for surface processingand tissue treatment. More particularly, the disclosure relates to aplasma catheter, a plasma system, and a method of manufacturing a plasmacatheter that facilitate efficient delivery of power to a distaltreatment portion of the catheter for creating highly energized plasmahaving sufficient energy to produce a clinical bipolar tissue effect.

Background of Related Art

Electrical discharges in dense media, such as liquids and gases at ornear atmospheric pressure, can, under appropriate conditions, result inplasma formation. Plasmas have the unique ability to create largeamounts of chemical species, such as ions, radicals, electrons,excited-state (e.g., metastable) species, molecular fragments, photons,and the like. The plasma species may be generated in a variety ofinternal energy states or external kinetic energy distributions bytailoring plasma electron temperature and electron density. In addition,adjusting spatial, temporal and temperature properties of the plasmacreates specific changes to the material being irradiated by the plasmaspecies and associated photon fluxes. Plasmas are also capable ofgenerating photons including energetic ultraviolet photons that havesufficient energy to initiate photochemical and photocatalytic reactionpaths in biological and other materials that are irradiated by theplasma photons.

SUMMARY

Plasmas have broad applicability and provide alternative solutions toindustrial, scientific and medical needs, especially workpiece (e.g.,tissue) surface treatment at any temperature range. Plasmas may bedelivered to the workpiece, thereby effecting multiple changes in theproperties of materials upon which the plasmas impinge. Plasmas have theunique ability to create large fluxes of radiation (e.g., ultraviolet),ions, photons, electrons and other excited-state (e.g., metastable)species which are suitable for performing material property changes withhigh spatial, material selectivity, and temporal control. Plasmas mayalso remove a distinct upper layer of a workpiece with little or noeffect on a separate underlayer of the workpiece or it may be used toselectively remove a particular tissue from a mixed tissue region orselectively remove a tissue with minimal effect to adjacent organs ofdifferent tissue type.

The plasma species are capable of modifying the chemical nature oftissue surfaces by breaking chemical bonds, substituting or replacingsurface-terminating species (e.g., surface functionalization) throughvolatilization, gasification or dissolution of surface materials (e.g.,etching). With proper techniques, material choices and conditions, onecan remove one type of tissue entirely without affecting a nearbydifferent type of tissue. Controlling plasma conditions and parameters(including S-parameters, V, I, Θ, and the like) allows for the selectionof a set of specific particles, which, in turn, allows for selection ofchemical pathways for material removal or modification as well asselectivity of removal of desired tissue type.

The present disclosure provides a plasma catheter including a tubularmember; a conductive cylindrical member; a first electrode; and a secondelectrode. The tubular member defines a longitudinal lumen therethroughand has a proximal portion and a distal portion. The conductivecylindrical member is disposed at the distal portion of the tubularmember. The first electrode is embedded in a first side of the tubularmember and coupled to the conductive cylindrical member. The secondelectrode is embedded in a second side of the tubular memberdiametrically opposed to the first side. The second electrode is offsetfrom the tubular member and aligned with a center axis defined by theconductive cylindrical member.

According to one aspect of the present disclosure, the conductivecylindrical member is configured to concentrate an electrical field atthe distal portion of the catheter such that an electrical fieldmagnitude between the first electrode and the second electrode at thedistal portion of the catheter is greater than an electrical fieldmagnitude between the first electrode and the second electrode at aportion of the catheter proximal of the distal portion of the catheter.

According to another aspect of the present disclosure, the secondelectrode is embedded in a bulge of the second side of the tubularmember.

According to another aspect of the present disclosure, the plasmacatheter further includes a ceramic tubular member, and the conductivecylindrical member is disposed about the ceramic tubular member.

According to another aspect of the present disclosure, the ceramictubular member includes mica, aluminum oxide, sapphire, zirconia, and/orpolytetrafluoroethylene.

According to another aspect of the present disclosure, the firstelectrode includes copper and the second electrode includes tungsten.

According to another aspect of the present disclosure, the firstelectrode and the conductive cylindrical member include an insulatinglayer.

According to another aspect of the present disclosure, the firstelectrode and the second electrode are arranged in a double helixstructure within at least a portion of the tubular member.

According to another aspect of the present disclosure, the double helixstructure is configured to produce an inductance that mitigates aparasitic capacitance between the first electrode and the secondelectrode.

The present disclosure also provides a plasma system including a plasmacatheter; an ionizable media source; and a generator. The plasmacatheter includes a tubular member; a conductive cylindrical member; afirst electrode; and a second electrode. The tubular member defines alongitudinal lumen therethrough and has a proximal portion and a distalportion. The conductive cylindrical member is disposed at the distalportion of the tubular member. The first electrode is embedded in afirst side of the tubular member and coupled to the conductivecylindrical member. The second electrode is embedded in a second side ofthe tubular member diametrically opposed to the first side. The secondelectrode is offset from the tubular member and aligned with a centeraxis defined by the conductive cylindrical member. The ionizable mediasource is configured to provide ionizable media to the plasma catheter.The generator is configured to provide power to the plasma catheter toignite the ionizable media to generate plasma.

According to another aspect of the present disclosure, an amount of thepower provided to a distal portion of the plasma catheter produces aclinical bipolar tissue effect on a workpiece, and the effect includesbiological decontamination, hemostasis, tissue necrosis, tissuevaporization, and/or ablation.

According to another aspect of the present disclosure, the ionizablemedia includes argon, helium, neon, krypton, xenon, radon, carbondioxide, nitrogen, hydrogen, and/or oxygen, in gaseous form.

According to another aspect of the present disclosure, the plasma systemfurther includes a precursor source configured to provide precursorfeedstocks to the plasma catheter.

According to another aspect of the present disclosure, at least aportion of the plasma catheter is arranged within a flexible endoscope.

The present disclosure also provides a method of manufacturing a plasmacatheter. The method includes embedding a first electrode in a firstside of a tubular member that defines a longitudinal lumen therethroughand has a proximal portion and a distal portion. The first electrode iscoupled to a conductive cylindrical member disposed at the distalportion of the tubular member. A second electrode is embedded in asecond side of the tubular member diametrically opposed to the firstside. The second electrode is offset from the tubular member and alignedwith a center axis defined by the conductive cylindrical member.

According to another aspect of the present disclosure, the method ofmanufacturing a plasma catheter further includes inserting a ceramictubular member into the distal portion of the tubular member, andpositioning the conductive cylindrical member around the ceramic tubularmember.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of thedisclosure and, together with a general description of the disclosuregiven above, and the detailed description of the embodiments givenbelow, serve to explain the principles of the disclosure, wherein:

FIG. 1 is a schematic diagram of a plasma system according to thepresent disclosure;

FIG. 2 is a front view of an embodiment of an electrosurgical generatoraccording to the present disclosure;

FIG. 3 is a schematic block diagram of an embodiment of theelectrosurgical generator of FIG. 2 according to the present disclosure;

FIG. 4 is a schematic view of a plasma device according to the presentdisclosure;

FIG. 5A is a perspective cross-sectional view of a distal portion of apartially-assembled plasma catheter of the plasma device of FIG. 4according to an embodiment of the present disclosure;

FIG. 5B is a cross-sectional view taken along line 5B of the distalportion of the partially-assembled plasma catheter of FIG. 5A accordingto an embodiment of the present disclosure;

FIG. 6 shows a perspective cross-sectional view of the catheter 404formed by double extrusion, according to an embodiment of the presentdisclosure;

FIG. 7A is a perspective cross-sectional view of the distal portion ofthe plasma catheter of the plasma device of FIG. 4 according to anembodiment of the present disclosure;

FIG. 7B is a perspective view of the distal portion of the plasmacatheter of the plasma device of FIG. 4 according to an embodiment ofthe present disclosure;

FIG. 8 shows an enlarged perspective cross-sectional view of the distalportion of the plasma catheter of the plasma device of FIG. 4 accordingto an embodiment of the present disclosure;

FIG. 9 shows an enlarged perspective view of the distal portion of theplasma catheter of the plasma device of FIG. 4 according to anembodiment of the present disclosure; and

FIG. 10 is a cross-sectional view of a proximal portion of the plasmacatheter of the plasma device of FIG. 4 according to an embodiment ofthe present disclosure.

DETAILED DESCRIPTION

Plasmas may be generated using electrical energy that is delivered aseither direct current (DC) electricity or alternating current (AC)electricity at frequencies from about 0.1 hertz (Hz) to about 100gigahertz (GHz), including radio frequency (“RF” from about 0.1 MHz toabout 100 MHz) and microwave (“MW” from about 0.1 GHz to about 100 GHz)bands, using appropriate generators, electrodes, and antennas. Choice ofexcitation frequency, the workpiece, as well as the electrical circuitsthat are used to deliver electrical energy to the workpiece affect manyproperties and requirements of the plasma. The performance of the plasmachemical generation, the delivery system and the design of theelectrical excitation circuitry are interrelated—as the choices ofoperating voltage, frequency and current levels, phase, and otherelectrical properties affect the electron temperature and electrondensity. Further, choices of electrical excitation and plasma devicehardware also determine how a given plasma system responds dynamicallyto the introduction of new ingredients to the host plasma gas or liquidmedia. For instance, isolation and/or reduction of capacitance betweentwo wires of a plasma device may be improved by employing a materialhaving a relatively low dielectric constant, such as polyfluorenyleneethynylene (PFE) or polytetrafluoroethylene (PTFE, for example, TEFLON),as a dialectric material forming a tubular member of the plasma device.

Plasma beams may be used to coagulate, cauterize, or otherwise treattissue through direct application of a high-energy plasma. Inparticular, kinetic energy transfer from the plasma to the tissue causeshealing, and thus, affects thermal coagulation of bleeding tissue.Plasma beam coagulation utilizes a handheld electrosurgical instrumenthaving one or more electrodes energizable by an electrosurgicalgenerator, which outputs a high-intensity electric field suitable forforming plasma using ionizable media (e.g., inert gas).

In some cases, electrical energy is delivered to a workpiece by way of abipolar plasma catheter that is sized to fit within a working channel ofa flexible endoscope and may be employed, for example, ingastrointestinal procedures. As used herein, the term “bipolar” refersto a plasma system that includes a handheld electrosurgical instrumenthaving both an active and a return electrode. The system does notinclude a separate return electrode coupled to the patient, thusisolating the patient from the electrosurgical generator.Electrosurgical energy is provided by a generator and forms an electricfield between the electrodes contained within the instrument. In thisconfiguration, plasma is generated within the instrument and isdelivered to the patient as gas is pushed out of the instrument.

The two electrodes or wires are disposed along a central lumen of thebipolar plasma catheter. In some cases, the central lumen may have arelatively small inner or outer diameter from about 2 millimeters (mm)to about 4 mm. Electrical RF energy passing through the electrodesdisposed in such proximity may give rise to significant capacitivecoupling between the two electrodes. Such parasitic coupling results ina loss of electrosurgical energy along the length of the catheter, whichin turn, produces insufficient power at the distal tip of the catheterand minor ionization of ionizable gas flowing down the lumen. Such minorionization, while perhaps useful for pre-ignition of monopolar plasmaenergy, may be insufficient to create direct tissue effects by bipolarplasma.

The present disclosure provides for a plasma catheter and a plasmacatheter system that overcome the drawbacks commonly associated withplacing multiple electrodes within a small diameter lumen of thecatheter. The plasma catheter according to the present disclosureincludes two electrodes embedded in diametrically opposed sides of atubular member (e.g., in respective bulges in the tubular member),thereby minimizing capacitive coupling between the two electrodes. At adistal portion of the catheter, a first one of the electrodes iselectrically coupled to a conductive cylindrical member, and a secondone of the electrodes is offset from the tubular member and aligned witha center of the conductive cylindrical member, thereby maximizing thedelivery of electrical energy between the two electrodes at the distalportion of the catheter.

As used herein, the term “diametrically opposed” refers to twoelectrodes being positioned opposite (or approximately opposite) oneother on opposite ends of a diameter of a circle as defined by a tubularmember. In a case where a tubular member forms an oval shape, the twoelectrodes may be diametrically opposed by being positioned opposite (orapproximately opposite) one other on opposite ends of the major axis ofthe oval formed by the tubular member, thereby maximizing the distancebetween the two electrodes and minimizing the capacitive couplingtherebetween.

Referring initially to FIG. 1, a plasma system 100 is disclosed. Thesystem 100 includes a plasma device 102 that is coupled to a generator104 (e.g., an electrosurgical generator), an ionizable media source 106and a precursor(s) source 108. Generator 104 includes any suitablecomponents for delivering power or matching impedance to plasma device102. More particularly, the generator 104 may be any radio frequencygenerator or other suitable power source capable of producing power toignite the ionizable media to generate plasma. The various examplecatheters described herein enable an amount of the power to be providedto the distal portion of the plasma catheter that produces a clinicalbipolar tissue effect on a workpiece, such as, for example, biologicaldecontamination, hemostasis, tissue necrosis, tissue vaporization,and/or ablation. The plasma device 102 may be utilized as anelectrosurgical pencil for application of plasma to tissue and thegenerator 104 may be an electrosurgical generator that is adapted tosupply the device 102 with electrical power at a frequency from about0.1 MHz to about 2,450 MHz and in another embodiment from about 1 MHz toabout 13.56 MHz. The plasma may also be ignited by using continuous orpulsed direct current (DC) electrical energy.

The precursor source(s) 108 may be a bubbler or a nebulizer configuredto aerosolize precursor feedstocks prior to introduction thereof intothe device 102. The precursor(s) source 108 may also be a microdropletor injector system capable of generating predetermined refined dropletvolume of the precursor feedstock from about 1 femtoliter to about 1nanoliter in volume. The precursor(s) source 108 may also include amicrofluidic device, a piezoelectric pump, or an ultrasonic vaporizer.

The system 100 provides a flow of plasma through the device 102 to aworkpiece “W” (e.g., tissue). Plasma feedstocks, which include ionizablemedia and precursor feedstocks, are supplied by the ionizable mediasource 106 and the precursor(s) source 108, respectively, to the plasmadevice 102. During operation, the precursor feedstock and the ionizablemedia are provided to the plasma device 102 where the plasma feedstocksare ignited to form plasma effluent containing ions, radicals, photonsfrom the specific excited species and metastables that carry internalenergy to drive desired chemical reactions in the workpiece “W” (e.g.,tissue) or at the surface thereof. The feedstocks may be mixed upstreamfrom the ignition point or midstream thereof (e.g., at the ignitionpoint) of the plasma effluent, as shown in FIG. 1 and described in moredetail below.

The ionizable media source 106 provides ionizable feedstock, alsoreferred to herein as ionizable media, to the plasma device 102.Suitable ionizable media include argon, helium, neon, krypton, xenon,radon, carbon dioxide, nitrogen, hydrogen, and/or oxygen, andcombinations thereof in liquid and/or gaseous form. The ionizable mediasource 106 is coupled to the plasma device 102 and may include a storagetank and a pump (not explicitly shown). These and other gases may beinitially in a liquid form that is gasified during application.

The precursor(s) source 108 provides precursor feedstock to the plasmadevice 102. The precursor feedstock may be either in solid, gaseous orliquid form and may be mixed with the ionizable media in any state, suchas solid, liquid (e.g., particulates or droplets), gas, and thecombination thereof. The precursor(s) source 108 may include a heater,such that if the precursor feedstock is liquid, it may be heated intogaseous state prior to mixing with the ionizable media.

In one embodiment, the precursors may be any chemical species capable offorming reactive species such as ions, electrons, excited-state (e.g.,metastable) species, molecular fragments (e.g., radicals) and the like,when ignited by electrical energy from the generator 104 or whenundergoing collisions with particles (electrons, photons, or otherenergy bearing species of limited and selective chemical reactivity)formed from ionizable media 106. More specifically, the precursors mayinclude various reactive functional groups, such as acyl halide,alcohol, aldehyde, alkane, alkene, amide, amine, butyl, carboxlic,cyanate, isocyanate, ester, ether, ethyl, halide, haloalkane, hydroxyl,ketone, methyl, nitrate, nitro, nitrile, nitrite, nitroso, peroxide,hydroperoxide, oxygen, hydrogen, nitrogen, and combination thereof. Inembodiments, the chemical precursors may be water, halogenoalkanes, suchas dichloromethane, tricholoromethane, carbon tetrachloride,difluoromethane, trifluoromethane, carbon tetrafluoride, and the like;peroxides, such as hydrogen peroxide, acetone peroxide, benzoylperoxide, and the like; alcohols, such as methanol, ethanol,isopropanol, ethylene glycol, propylene glycol, alkalines such as NaOH,KOH, amines, alkyls, alkenes, and the like. Such chemical precursors maybe applied in substantially pure, mixed, or soluble form.

The precursors and their functional groups may be delivered to a surfaceto react with the surface species (e.g., molecules) of the workpiece“W.” In other words, the functional groups may be used to modify orreplace existing surface terminations of the workpiece “W.” Thefunctional groups react readily with the surface species due to theirhigh reactivity and the reactivity imparted thereto by the plasma. Inaddition, the functional groups are also reacted within the plasmavolume prior to delivering the plasma volume to the workpiece.

Some functional groups generated in the plasma can be reacted in situ tosynthesize materials that subsequently form a deposition upon thesurface. This deposition may be used for stimulating healing, killingbacteria, and increasing hydrophilic or hydroscopic properties. Inaddition, deposition of certain function groups may also allow forencapsulation of the surface to achieve predetermined gas/liquiddiffusion, e.g., allowing gas permeation but preventing liquid exchange,to bond or stimulate bonding of surfaces, or as a physically protectivelayer.

With reference to FIG. 2, a front face 202 of the generator 104 isshown. The generator 104 may be any suitable type (e.g.,electrosurgical, microwave, etc.) and may include a plurality ofconnectors 204, 206, 208, 210, 212, 214, and 216 to accommodate varioustypes of electrosurgical instruments (e.g., electrosurgical forceps,electrosurgical pencils, ablation probes, etc.) in addition to a plasmainstrument (e.g., plasma instrument 102, not shown in FIG. 2).

The generator 104 includes a user interface 218 having one or moredisplay screens 220, 222, 224 for providing the user with variety ofoutput information (e.g., intensity settings, treatment completeindicators, etc.). Each of the screens 220, 222, 224 is associated witha corresponding subset of the connectors 204, 206, 208, 210, 212, 214,and 216, as shown in FIG. 2 and as described in further detail below.The generator 104 includes suitable input controls (e.g., buttons,activators, switches, touch screen, etc.) for controlling the generator104. The display screens 220, 222, 224 are also configured as touchscreens that display a corresponding menu for the electrosurgicalinstruments (e.g., a plasma instrument, etc.). The user then adjustsinputs by simply touching corresponding menu options.

Screen 220 controls monopolar output and the devices connected to theconnectors 204 and 206. Connector 204 is configured to couple to amonopolar electrosurgical instrument (e.g., electrosurgical pencil) andconnector 206 is configured to couple to a foot switch (not shown inFIG. 2). The foot switch provides for additional inputs (e.g.,replicating inputs of the generator 104). Screen 222 controls monopolar,plasma and bipolar output and the devices connected to the connectors210 and 212. Connector 210 is configured to couple to other monopolarinstruments. Connector 212 is configured to couple to a plasmainstrument (e.g., plasma instrument 102, not shown in FIG. 2).

Connector 208 may be used to connect to one or more return electrodepads (not shown in FIG. 2). The return electrode pad may be coupled tothe generator 104 via a return pad cable, which is coupled to theconnector 208 via a plug (not shown in FIG. 2). The return electrode padmay be coupled to a polarization controller (not shown), which in turnis coupled to the connector 208. Screen 224 controls plasma proceduresperformed by a plasma instrument (e.g., plasma instrument 102) that maybe plugged into the connectors 214 and 216.

FIG. 3 shows a schematic block diagram of the generator 104 configuredto output electrosurgical energy. The generator 104 includes acontroller 302, a power supply 304, and a radio-frequency (RF) amplifier306. The power supply 304 may be a high voltage, DC power supplyconnected to an AC source (e.g., line voltage) and provides highvoltage, DC power to the RF amplifier 306 via leads 304 a and 304 b,which then converts high voltage, DC power into treatment energy (e.g.,electrosurgical or microwave) and delivers the energy to the activeterminal 308. The energy is returned thereto via the return terminal310. The active and return terminals 308 and 310 are coupled to the RFamplifier 306 through an isolation transformer 312. The RF amplifier 306is configured to operate in a plurality of modes, during which thegenerator 104 outputs corresponding waveforms having specific dutycycles, peak voltages, crest factors, etc. It is envisioned that inother embodiments, the generator 104 may be based on other types ofsuitable power supply topologies.

The controller 302 includes a processor 314 operably connected to amemory 316, which may include transitory type memory (e.g., RAM) and/ornon-transitory type memory (e.g., flash media, disk media, etc.). Theprocessor 314 includes an output port that is operably connected to thepower supply 304 and/or RF amplifier 306 allowing the processor 314 tocontrol the output of the generator 104 according to either open and/orclosed control loop schemes. A closed loop control scheme is a feedbackcontrol loop, in which a plurality of sensors measure a variety oftissue and energy properties (e.g., tissue impedance, tissuetemperature, output power, current and/or voltage, etc.), and providefeedback to the controller 302. The controller 302 then signals thepower supply 304 and/or RF amplifier 306, which adjusts the DC and/orpower supply, respectively. Those skilled in the art will appreciatethat the processor 314 may be substituted by using any logic processor(e.g., control circuit) adapted to perform the calculations and/or setof instructions described herein including, but not limited to, fieldprogrammable gate array, digital signal processor, and combinationsthereof.

The generator 104 according to the present disclosure includes aplurality of sensors 318, e.g., an RF current sensor 318 a, and an RFvoltage sensor 318 b. Various components of the generator 104, namely,the RF amplifier 306, the RF current and voltage sensors 318 a and 318b, may be disposed on a printed circuit board (PCB). The RF currentsensor 318 a is coupled to the active terminal 308 and providesmeasurements of the RF current supplied by the RF amplifier 306. Inembodiments the RF current sensor 318 a may be coupled to the returnterminal 310. The RF voltage sensor 318 b is coupled to the active andreturn terminals 308 and 310 provides measurements of the RF voltagesupplied by the RF amplifier 306. In embodiments, the RF current andvoltage sensors 318 a and 318 b may be coupled to active and returnleads 306 a and 306 b, which interconnect the active and returnterminals 308 and 310 to the RF amplifier 306, respectively.

The RF current and voltage sensors 318 a and 318 b provide the sensed RFvoltage and current signals, respectively, to the controller 302, whichthen may adjust output of the power supply 304 and/or the RF amplifier306 in response to the sensed RF voltage and current signals. Thecontroller 302 also receives input signals from the input controls ofthe generator 104 and/or the plasma instrument 102. The controller 302utilizes the input signals to adjust the power output of the generator104 and/or performs other control functions thereon.

FIG. 4 is a schematic view of the plasma device 102 according to thepresent disclosure. With reference to FIGS. 1 and 4, the precursor(s)source 108 and the ionizable media source 106 may be coupled to theplasma device 102 via tubing 116 and 118, respectively. The tubing 116and 118 may be combined into unified tubing to deliver a mixture of theionizable media and the precursor feedstock to the device 102 at aproximal end thereof. This allows for the plasma feedstocks, e.g., theprecursor feedstock and the ionizable gas, to be delivered to the plasmadevice 102 simultaneously prior to ignition of the mixture therein.

In another embodiment, the ionizable media source 106 and theprecursor(s) source 108 may be coupled to the plasma device 102 via thetubing 116 and 118 at separate connections, such that the mixing of thefeedstocks occurs within the plasma device 102 upstream from theignition point. In other words, the plasma feedstocks are mixedproximally of the ignition point, which may be any point between therespective sources 106 and 108 and the plasma device 102, prior toignition of the plasma feedstocks to create the desired mix of theplasma effluent species for each specific surface treatment on theworkpiece “W.”

In a further embodiment, the plasma feedstocks may be mixed midstream,e.g., at the ignition point or downstream of the plasma effluent,directly into the plasma. It is also envisioned that the ionizable mediamay be supplied to the device 102 proximally of the ignition point,while the precursor feedstocks are mixed therewith at the ignitionpoint. In a further illustrative embodiment, the ionizable media may beignited in an unmixed state and the precursors may be mixed directlyinto the ignited plasma. Prior to mixing, the plasma feedstocks may beignited individually. The plasma feedstock is supplied at apredetermined pressure to create a flow of the medium through the device102, which aids in the reaction of the plasma feedstocks and produces aplasma effluent. The plasma according to the present disclosure isgenerated at or near atmospheric pressure under normal atmosphericconditions.

With continued reference to FIG. 4, the device 102 includes a handle 402and a catheter 404 having a proximal portion 406 that is coupled to thehandle 402 and a distal portion 408. The catheter 404 includes a tubularmember 414 defining a lumen 410 therein and extending the entire lengththereof and terminating in an opening 412 at the distal portion 416 ofthe distal portion 408. The catheter 404 may have a diameter from about2 mm to about 10 mm, in embodiments, from about 3 mm to about 5 mm (forexample, for compatibility with a working channel of an endoscope havinga diameter of 1.6 mm, 2.4 mm, or 3.8 mm), allowing the device 102 to beinserted through operating ports for application of the plasma effluent120 at the operating site during endoscopic or endoluminal procedures orthrough natural body orifices.

In one exemplary embodiment, the distal portion 408 is configured forcontrolled deflection. A pull-wire (not shown in FIG. 4) or anothersuitable actuation mechanism extends from the handle 402 at the proximalend of the device 102 through a lumen in the catheter 404 and isfastened to the distal portion 408. The pull-wire is movable from afirst generally relaxed position wherein the distal portion 408 isdisposed in a generally longitudinally-aligned position relative to theproximal portion 406 to a second retracted or tensed position whereinthe distal portion 408 flexes (e.g., deflects) from the proximal portion406 at a desired angle as shown in FIG. 4.

The distal portion 408 is constructed to be more flexible than theproximal portion 406, such that when the handle 402 is pulled back orotherwise actuated, the pull-wire bends the distal portion 408 from anundeflected position to a deflected position. The pull-wire may beattached to the outside of a ceramic tubular member 510 (FIG. 7A), orthe pull-wire may be an additional polymer fiber attached to the lumenstructure 410 and free from the lumen 410 at a proximal end of theflexed portion of the catheter 404. In particular, the proximal portion406 may include a wire or other support materials (not shown) therein toprovide tensile strength to the catheter 404 while still maintainingflexibility for maneuvering through a vascular system. The distalportion 408 is formed from a flexible biocompatible material such aspolytetrafluoroethylene, polyurethane, polyimide, polyether block amide(PEBAX), and the like to allow for maneuverability thereof.

The device 102 includes two or more electrodes 504 and 506 (e.g., areturn electrode and an active or working electrode, respectively),which are described in further detail below, with respect to FIGS.5A-10. In embodiments, the electrodes 504 and 506 may be formed as wireelectrodes (e.g., pointed tip), and may be disposed within the tubularmember 414 so as to minimize capacitive coupling between the electrodes504 and 506 at the proximal portion 406 while maximizing the electricfield between the external and internal conductors at the distal portion416 of the catheter 404 to ignite ionizable media and form plasma.

The electrodes 504 and 506 are disposed through the catheter 404 and areconnected to the generator 104 via electrical cable 122. The ionizablemedia source 106 and the precursor(s) source 108 may include variousflow sensors and controllers (e.g., valves, mass flow controllers, etc.)to control the flow of ionizable media to the device 102. In particular,the lumen 410 is in gaseous and/or liquid communication with theionizable media source 106 and the precursor(s) source 108 allowing forthe flow of ionizable media and precursor feedstocks to flow through thecatheter 404 to the distal portion 408. The ionizable media inconjunction with the precursor feedstocks is ignited by application ofenergy through the electrodes 504 and 506 to form the plasma plume 120exiting through the opening 412.

FIG. 5A is a perspective cross-sectional view of a distal portion 416 ofthe plasma catheter 404 in a partially-assembled form. The catheter 404includes the tubular member 414 that defines the lumen 410 by which theionizable media is delivered. The catheter 404 also includes a firstelectrode 504 and a second electrode 506. The first and secondelectrodes 504 and 506 may be formed from any suitable electricallyconducting material. In example embodiments, the electrodes 504 and 506may be formed from wires that have an inductance rating at about 473 kHzof approximately 7.37 pH and a capacitance at 1 MHz of 32.0 pF to yielda cable self resonance of about 10.4 MHz. A diameter of the firstelectrode 504 and/or a diameter of the second electrode 506 may be, forexample, from about 0.001 inches to about 0.020 inches, in embodimentsfrom about 0.005 inches to about 0.015 inches. In some exemplaryembodiments herein, at least a portion of the first electrode 504 and/orthe second electrode 506 may be covered by an insulating material.

As shown in FIG. 5A, the first electrode 504 is embedded in a first side514 of the tubular member 414, and the second electrode 506 is embeddedin a second side 516 of the tubular member 414, which is diametricallyopposed to the first side 514. In embodiments, the second electrode 506may be embedded in a bulge 518 extending either the lumen 410. Infurther embodiments, the bulge 518 may extend outwardly and be disposedoutside the lumen 410. The first electrode 504 may be embedded in thefirst side 514 without being embedded in a bulge, other variations onthis configuration are contemplated such as only one of the electrodes504, 506 being disposed within the bulge 518 or alternatively, bothelectrodes 504, 506 being disposed within their respective bulges 518 orin further embodiments, both electrodes 504, 506 being directly disposedwithin the tubular member 414.

At the distal portion 416 of the catheter 404, the second electrode 506is offset from the tubular member 414 and is arranged so as to besubstantially aligned with a center of the lumen 410, which maysubstantially align with a center of a conductive cylindrical member 512as described below with respect to FIGS. 7A and 7B. The second electrode506 may be offset by skiving a portion of the tubular member 414, namelythe bulge 518, and then bending a distal portion of the second electrode506 to align in the desired configuration.

Arrangement of the first electrode 504 and the second electrode 506 indiametrically opposed sides 514, 516 of the tubular member 414throughout the proximal portion 406 of the catheter 404 maximizes adistance between the first electrode 504 and the second electrode 506.This configuration of the electrodes 504 and 506 minimizes capacitivecoupling between the first electrode 504 and the second electrode 506.As described in further detail below in connection with FIGS. 7A and 7B,at a distal portion of the catheter 404, the first electrode 504 and thesecond electrode 506 are offset from their respective sides of thetubular member 414 and are arranged so as to maximize the delivery ofelectrical energy between the first and second electrodes 504 and 506 atthe distal portion 416 of the catheter 404.

FIG. 5B shows a cross-sectional view taken along line 5B of the distalportion of the plasma catheter 404 in a partially-assembled form. Asapparent from FIG. 5B, the first electrode 504 is embedded in the firstside 514 of the tubular member 414 and the second electrode 506 isembedded in a bulge 518 of the second side 516 of the tubular member414, the bulge 518 and the second side 516 being diametrically opposedto the first side 514. The lumen 410 is disposed through the catheter404.

The plasma catheter 404 can be manufactured using single or multipleextrusions. In a single extrusion procedure, the electrodes 504 and 506are extruded within a sheath material (e.g., a polymer) in a singleextrusion, thereby disposing the electrodes 504 and 506 within thetubular member 414 that is formed from the sheath material and definesthe lumen 410 therein. Alternatively, in a double extrusion, theelectrodes 504 and 506 are extruded in two separate extrusion steps.Initially, the electrode 506 can be extruded within a first sheathmaterial (e.g., polytetrafluoroethylene) in a first extrusion step,thereby disposing the electrode 506 within a bulge 518 formed from thefirst sheath material. Then, the electrode 506, once disposed within thebulge 518, is fed together with the electrode 504 into an extruder to beextruded within a second sheath material (e.g., polyfluorenyleneethynylene (PFE) or another suitable polymer) in a second extrusionstep, thereby disposing the electrodes 504 and 506 within the tubularmember 414 that is formed from the second sheath material and definesthe lumen 410 therein.

FIG. 6 shows a perspective cross-sectional view of the catheter 404formed by a double extrusion procedure. As shown in FIG. 6, the catheter404 includes the electrode 504 disposed within the tubular member 414and the electrode 506 disposed within the bulge 518. For illustrativepurposes, in FIG. 6 the electrode 506 and the bulge 518, which areformed in the first extrusion step, are shown as extending beyond theelectrode 504 and tubular member 414.

Reference will now be made to FIGS. 7A, 7B, 8, and 9, which show thedistal portion of the plasma catheter 404. The plasma catheter 404includes a ceramic tubular member 510, which is inserted into the distalportion 416 of the catheter 404 and a metallic ring 512 is positionedaround and/or secured to an outside of the ceramic tubular member 510.The ceramic tubular member 510 may be formed from any suitableinsulating materials capable of withstanding high-temperatures, such as,for instance, mica, aluminum oxide, sapphire, zirconia,polytetrafluoroethylene (for example, TEFLON), and combinations thereof,selected for high temperature, high dielectric strength, and relativelyhigh dielectric constant, for example.

At the distal portion 416 of the catheter 404, the first electrode 504is electrically coupled to the metallic ring 512. The second electrode506 is offset from the tubular member 414 and is substantially alignedwith a center of the metallic ring 512, which encircles the secondelectrode 506. In embodiments, the first electrode 504 may be formedfrom a first metal including, but not limited to, copper and may beelectrically soldered or welded to the metallic ring 512 at the distalportion 416 of the catheter 404, and the second electrode 506 may beformed from a second metal sufficient to handle relatively high energylevels (e.g., an energy level sufficient to produce a clinical bipolartissue effect), such as by way of example and not limitation, tungstenor tungsten alloy with thorium.

The metallic ring 512 is configured to concentrate an electrical fieldat a distal portion 416 of the catheter 404 (e.g., at distal portion802, where the metallic ring 512 encircles the second electrode 506),such that an electrical field magnitude between the first electrode 504and the second electrode 506 at the distal portion 416 of the catheter404 is greater than an electrical field magnitude between the firstelectrode 504 and the second electrode 506 at the proximal portion 406of the catheter 404 allowing for ionization of the ionizable media.

In embodiments, the catheter 404 may include multiple metallic rings 512and/or scalloped metallic rings. In this case, at the distal portion 416of the catheter, the first electrode 504 is electrically coupled to eachof the metallic rings 512, and the second electrode 506 is offset fromthe tubular member 414 and aligned with the respective centers of eachof the metallic rings 512.

The metallic ring 512 may be formed as a layer (e.g., as a metal trace,printed conducting ink, and/or foil) so as to concentrate the electricfield on the outside of the ceramic tubular member 510, to maximize theelectrical communication between the first electrode 504 and the secondelectrode 506 at the distal portion 416 of the catheter 404. Inembodiments, the metallic ring 512 may be formed such that its width ina direction perpendicular to a central axis of the lumen 410 is lessthan its width in a direction parallel to a central axis of the lumen410. In further embodiments herein, the metallic ring 512 may be coveredby an insulating material and/or the metallic ring 512 may have asaw-toothed edge.

The first electrode 504 and the second electrode 506 of the catheter 404may also be arranged in a double helix structure in at least a proximalportion 406 of the catheter 404, thereby producing an inductance thatmitigates a parasitic capacitance created by the parallel electrodes504, 506 used in the catheter 404. In some embodiments, a parasiticcapacitance between the first electrode 504 and the second electrode 506may be less than 4 picoFarads per foot of length.

With reference to FIG. 10, which shows a cross-sectional view of thecatheter 404, the electrodes 504 and 506 are operatively connected tothe generator 104 via connectors 308 and 310, respectively. Theelectrodes 504 and 506 extend from the connectors 308 and 310,respectively, for a distance A, which can be optimally controlled by thelocation of connectors 308 and 310, and may be from approximately 0.1inches to approximately 6 inches. The electrodes 504 and 506 are thenhelix wound in a wound portion 1014, which may be from approximately 7feet or more, depending upon a desired cable inductance and capacitance.Alternatively, the wound portion 1014 may extend from the connectors 308and 310 without extending the electrodes 504 and 506 for the distance A.

The wound portion 1014, along catheter length B, can be of any lengthdepending on geometric configuration and physical properties (e.g.,tensile strength, flexibility, etc.) of materials used in manufacturingof catheter components. More specifically the electrodes 504 and 506 areoriented in a double helix which includes two congruent helixes with thesame axis, differing by a translation along the axis. The electrodes 504and 506 may be oriented in a plurality of other arrangements which wrapthe electrodes 504 and 506 around themselves. The arrangement of theelectrodes 504 and 506 in a double helix orients the opposing electricalfields generated by the electrosurgical RF energy passing therethroughto mitigate and/or cancel out thereby minimizing the amount of loststray electrical RF energy.

With continued reference to FIG. 10 and the portion 1014, the distanceD, which represents the distance between one apex of one helix and anearest apex of another helix, may be, for example, approximately ½inch. The distance E, which is the distance between two apexes of thesame helix may be, for example, approximately 1 inch. The outer diameterF of the catheter 404 may, for example, be about ⅜ of an inch.

The catheter 404, as illustrated in FIG. 10, provides a transmissionmedium to deliver RF energy from the generator 104 to a tissue site. Thecatheter 404 represents one example of a preferred embodiment for the RFtransmission medium, which reduces the radiated RF electrical field andmaximizes the applied clinical treatment energy delivered to the tissuesite. The dimensions A, B, C, D, E and F of FIG. 10 form a uniqueproximal geometric relationship in three dimensional space to controlthe electrical field coupling between the active and return outputterminals of the generator 104 to significantly reduce the electricalfield radiation by field cancellation.

The physical dimensions A, B, C, D, E and F are interdependent andoptimized to provide a low loss inductive and capacitive transmissionmedium, which in addition to controlling the electrical field, reducesuncontrolled capacitive coupling caused by stray RF radiation. Inparticular, the following equations (1) and (2) illustrate theinterdependent relationship of dimensions A, B, C, D, E and F withrespect to inductive and capacitive properties of the catheter 404.

Inductance=B(10.16×10̂−9)Ln[(2×D)/d)]+2(A+C)(μH/in. for specifiedwire)  (1)

Capacitance=[(B×(0.7065×10̂−12))/Ln[(2×D)/d]]er  (2)

In equations (1) and (2), d denotes diameter of the wire (e.g.,electrodes 504, 506), er denotes the dielectric constant of the wireinsulator. Further, E=2×D, the ratio of E to D allows to establish acontinuum of the helix configuration and F=k×D, where k is a constantfrom about 0.5 to about 1.5.

Although not shown in FIG. 10, at the distal portion 416 of the catheter404, the electrodes 504 and 506 may be unwound and disposed in themanner described above in connection with FIGS. 5A, 5B, 6, 7A, 7B, 8,and 9, so as to maximize the delivery of electrical energy between thetwo electrodes at the distal portion 416 of the catheter 404. Theelectrodes 504 and 506 extend a distance C from the portion 1014 to thedistal portion 408 in an unwound state. The initial length A of theelectrodes and the unwound state length C are maintained relativelyconsistent with varying lengths of wire with length of the wound portion1014 varying for different overall lengths.

The catheter 404 according to the present disclosure orients theelectrodes 504 and 506 so that the electrical fields generatedtherethrough are mitigated and/or substantially canceled (except at thedistal portion 416), thereby reducing the amount of leaked stray RFenergy. More specifically, placement and orientation of the electrodes504 and 506 in the manner discussed above provides for close proximityof electrical fields generated during transmission of electrosurgical RFenergy and maximizes amount of energy delivered to the treatment site.Reducing the electrical fields also increases safety of personnel andthe patient.

Reduced RF radiation decreases capacitive and RF field leakage andimproves RF control of the delivered energy. Reduced RF radiation alsodecreases RF transmission loss and improves efficiency of the generator104 by reducing RF harmonic component, minimizing corruption of the RFsource and reducing peripheral conductive and radiative emissions.Further, reducing RF radiation also decreases the RF noise to additionalequipment found in the room, such as patient monitoring equipment.

Although the illustrative embodiments of the present disclosure havebeen described herein with reference to the accompanying drawings, it isto be understood that the disclosure is not limited to those preciseembodiments, and that various other changes and modifications may beeffected therein by one skilled in the art without departing from thescope or spirit of the disclosure.

What is claimed is:
 1. A plasma catheter, comprising: a tubular memberdefining a longitudinal lumen therethrough and having a proximal portionand a distal portion; a conductive cylindrical member disposed at thedistal portion of the tubular member; a first electrode embedded in afirst side of the tubular member and coupled to the conductivecylindrical member; and a second electrode embedded in a second side ofthe tubular member diametrically opposed to the first side, the secondelectrode being offset from the tubular member and aligned with a centeraxis defined by the conductive cylindrical member.
 2. The plasmacatheter of claim 1, wherein the conductive cylindrical member isconfigured to concentrate an electrical field at the distal portion ofthe catheter such that an electrical field magnitude between the firstelectrode and the second electrode at the distal portion of the catheteris greater than an electrical field magnitude between the firstelectrode and the second electrode at a portion of the catheter proximalof the distal portion of the catheter.
 3. The plasma catheter of claim1, wherein the second electrode is embedded in a bulge of the secondside of the tubular member.
 4. The plasma catheter of claim 1, furthercomprising a ceramic tubular member, wherein the conductive cylindricalmember is disposed about the ceramic tubular member.
 5. The plasmacatheter of claim 4, wherein the ceramic tubular member includes atleast one of mica, aluminum oxide, sapphire, zirconia, orpolytetrafluoroethylene.
 6. The plasma catheter of claim 1, wherein thefirst electrode includes copper and the second electrode includestungsten.
 7. The plasma catheter of claim 1, wherein the first electrodeand the conductive cylindrical member include an insulating layer. 8.The plasma catheter of claim 1, wherein the first electrode and thesecond electrode are arranged in a double helix structure within atleast a portion of the tubular member.
 9. The plasma catheter of claim8, wherein the double helix structure is configured to produce aninductance that mitigates a parasitic capacitance between the firstelectrode and the second electrode.
 10. A plasma system comprising: aplasma catheter that includes: a tubular member defining a longitudinallumen therethrough and having a proximal portion and a distal portion; aconductive cylindrical member disposed at the distal portion of thetubular member; a first electrode embedded in a first side of thetubular member and coupled to the conductive cylindrical member; and asecond electrode embedded in a second side of the tubular memberdiametrically opposed to the first side, the second electrode beingoffset from the tubular member and aligned with a center axis defined bythe conductive cylindrical member; an ionizable media source configuredto provide ionizable media to the plasma catheter; and a generatorconfigured to provide power to the plasma catheter to ignite theionizable media to generate plasma.
 11. The plasma system of claim 10,wherein an amount of the power provided to a distal portion of theplasma catheter produces a clinical bipolar tissue effect on aworkpiece, the effect including at least one of biologicaldecontamination, hemostasis, tissue necrosis, tissue vaporization, orablation.
 12. The plasma system of claim 10, wherein the ionizable mediaincludes at least one of argon, helium, neon, krypton, xenon, radon,carbon dioxide, nitrogen, hydrogen, or oxygen, in gaseous form.
 13. Theplasma system of claim 10, further comprising a precursor sourceconfigured to provide precursor feedstocks to the plasma catheter. 14.The plasma system of claim 10, wherein at least a portion of the plasmacatheter is arranged within a flexible endoscope.
 15. A method ofmanufacturing a plasma catheter, the method comprising: embedding afirst electrode in a first side of a tubular member that defines alongitudinal lumen therethrough and has a proximal portion and a distalportion; coupling the first electrode to a conductive cylindrical memberdisposed at the distal portion of the tubular member; embedding a secondelectrode in a second side of the tubular member diametrically opposedto the first side; and offsetting the second electrode from the tubularmember and aligning the second electrode with a center axis defined bythe conductive cylindrical member.
 16. The method of claim 15, furthercomprising: inserting a ceramic tubular member into the distal portionof the tubular member; and positioning the conductive cylindrical memberaround the ceramic tubular member.